Present treatment of Rheumatoid Arthritis is performed by several methods which include anti-inflammatory agents, steroids, immuno-suppressive and cytotoxic agents, radiation treatment by beam method, and surgery. Each method has its drawbacks. Of these methods, radiation beam treatment has been shown to suppress the inflamed synovium and palliate the patient's pain. There are, however, adverse effects to surrounding hard and soft tissue. The objective of this proposed work is to develop a glass matrix containing an activatable beta emitting isotope with a treatment distance of 1 to 3 mm. When injected into the joint, the microspheres will permit a localized irradiation of the diseased area leading to results comparable to that provided by surgery. Once the radioactivity has decayed, the microspheres will dissolve and absorbed into the body over a 3 to 6 month time period.